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You searched for: creator:"P Walker"
[audio]Patrick Walker : Scanning Patern V_2 Various Artists - P Walker
Patrick Walker : Scanning Pattern V2 Feat : Sugar Experiment Station, Steevio, Neil Landstrumm, wee djs, patrick walker, (i)sodyne, lodestar, (a)pendics shuffle, B*Wilder, (1)S01, Elexx, Mark Henning, Digital Mix Created using Ableton V5.03 Radium Midi controllers, Line 6 Echo Pod + Various FX, mixed and recorded 100% Live @ AVXR H/Q April 2006. Dub, Electro, Hypnotic, Abstract, Techno w grimey electronix, ill riddems, broken machines...
Keywords: techno, minimal, netlabel, neil landstrumm, tobias Schmidt, elexx, patrick walker, steevio, mindtours, (a)pendics shuffle, Mark Henning, Avionix, electro, wee djs, dub, microhouse, crackhouse, detroit, hard techno, electronic
Downloads: 1,238
[texts]The BBN Manifesto - Terry P. Walker
In this manifesto I review the status of standard BBN in light of recent observational data (e.g., QSO deuterium and Izotov etal. helium-4).
Downloads: 10
[texts]J.P. Walker & Co. general hardware merchants, King Street, Hamilton, C.W. [microform] - J. P. Walker & Co
Cover title
Keywords: Hardware; Quincaillerie
Downloads: 188
[texts]The Merchant's Calculator, Or New, Complete, and Extended Ready Reckoner, Adapted to the Use of ... - C P. Walker
Book digitized by Google from the library of the University of Michigan and uploaded to the Internet Archive by user tpb.
Downloads: 223
[texts]Catalogue of paintings, engravings, and photographs at the "Walker Homestead", Topsham, Maine. - Wildes P. Walker (Topsham, Me.)

Keywords: Art--Catalogs; Engraving--Catalogs; Photographs--Catalogs
Downloads: 250
[texts]Proceedings in the Quo Warranto Case of the State Ex Relatione the Attorney-general Vs. Thomas P ... - Thomas P. Walker , South Carolina
Book digitized by Google from the library of Harvard University and uploaded to the Internet Archive by user tpb.
Downloads: 137
[texts]Constraints on the Cosmological Relativistic Energy Density - Andrew R. Zentner
We discuss bounds on the cosmological relativistic energy density as a function of redshift, reviewing the big bang nucleosynthesis and cosmic microwave background bounds, updating bounds from large scale structure, and introducing a new bound from the magnitude-redshift relation of Type Ia supernovae. We conclude that the standard and well-motivated assumption that relativistic energy is negligible during recent epochs is not necessitated by extant data...
Downloads: 5
[texts]New Coordinate Systems for Axisymmetric Black Hole Collisions - S. R. Brandt
We describe a numerical grid generating procedure to construct new classes of orthogonal coordinate systems that are specially adapted to binary black hole spacetimes. The new coordinates offer an alternative approach to the conventional \v{C}ade\v{z} coordinates, in addition to providing a potentially more stable and flexible platform to extend previous calculations of binary black hole collisions.
Downloads: 3
[texts]New Coordinate Systems for Axisymmetric Black Hole Collisions - P. Anninos
We describe a grid generation procedure designed to construct new classes of orthogonal coordinate systems for binary black hole spacetimes. The computed coordinates offer an alternative approach to current methods, in addition to providing a framework for potentially more stable and accurate evolutions of colliding black holes. As a particular example, we apply our procedure to generate appropriate numerical grids to evolve Misner's axisymmetric initial data set representing two equal mass blac...
Downloads: 15
[texts]Global Constraints On Key Cosmological Parameters - G. Steigman
Data from Type Ia supernovae, along with X-ray cluster estimates of the universal baryon fraction and Big Bang Nucleosynthesis (BBN) determinations of the baryon-to-photon ratio, are used to provide estimates of several global cosmological parameters at epochs near zero redshift. We show that our estimate of the present baryon density is in remarkably good agreement with that inferred from BBN at high redshift, provided the primordial abundance of deuterium is relatively low and the Universe is ...
Downloads: 2
[texts]The Supernova Relic Neutrino Background - M. Kaplinghat
An upper bound to the supernova relic neutrino background from all past Type II supernovae is obtained using observations of the Universal metal enrichment history. We show that an unambiguous detection of these relic neutrinos by the Super-Kamiokande detector is unlikely. We also analyze the event rate in the Sudbury Neutrino Observatory (where coincident neutrons from anti-nu_e + D --> n + n + e+ might enhance background rejection), and arrive at the same conclusion...
Downloads: 8
[texts]Nucleosynthesis in Power-Law Cosmologies - M. Kaplinghat
We have recently considered cosmologies in which the Universal scale factor varies as a power of the age of the Universe and concluded that they cannot satisfy the observational constraints on the present age, the magnitude-redshift relation for SN Ia, and the primordial element (D, He3, He4, and Li7) abundances. This claim has been challenged in a proposal that suggested a high baryon density model (Omega_B*h*h = 0.3) with an expansion factor varing linearly with time could be consistent with t...
Downloads: 12
[texts]Observational Constraints On Power-Law Cosmologies - M. Kaplinghat
In a class of models designed to solve the cosmological constant problem by coupling scalar or tensor classical fields to the space-time curvature, the universal scale factor grows as a power law in the age, $a \propto t^\alpha$, regardless of the matter content or cosmological epoch. We investigate constraints on such "power-law cosmologies" from the present age of the Universe, the magnitude-redshift relation, and from primordial nucleosynthesis...
Downloads: 10
[texts]The observability of gamma-rays from neutralino annihilations in Milky Way substructure - Savvas M. Koushiappas
We estimate the probability of detecting gamma-rays from the annihilation of neutralino dark matter in dense, central regions of Milky Way substructure. We characterize Galactic substructure statistically based on Monte Carlo realizations of the formation of a Milky Way-like halo using a semi-analytic method that has been calibrated against the results of high-resolution N-body simulations. We find that it may be possible for the upcoming experiments GLAST and VERITAS, working in concert, to det...
Downloads: 5
[texts]Primordial Nucleosynthesis: Theory and Observations - Keith A. Olive
We review the Cosmology and Physics underlying Primordial Nucleosynthesis and survey current observational data in order to compare the predictions of Big Bang Nucleosynthesis with the inferred primordial abundances. From this comparison we report on the status of the consistency of the standard hot big bang model, we constrain the universal density of baryons (nucleons), and we set limits to the numbers and/or effective interactions of hypothetical new "light" particles (equivalent massless neu...
Downloads: 8
[texts]Gamma-rays From Neutralino Annihilation in Milky Way Substructure: What Can We Learn? - Savvas M. Koushiappas
We estimate the probability of detecting gamma-rays from the annihilation of neutralino dark matter in the substructure of the Milky Way. We characterize substructure statistically based on Monte Carlo realizations of the formation of a Milky Way-like halo using semi-analytic methods that have been calibrated against N-body simulations. We find that it may be possible for the upcoming GLAST and VERITAS experiments, working in concert, to detect gamma-rays from dark matter substructure if $\Mchi ...
Downloads: 5
[texts]Cosmic Microwave Background constraint on residual annihilations of relic particles - Patrick McDonald
Energy injected into the Cosmic Microwave Background at redshifts z
Downloads: 24
[texts]Mississippi Law Journal May 1961 Book 3 (Volume 32) - William P. Murphy; Earl T. Thomas; Joel P. Walker, Jr.

Keywords: Mississippi; Law; History; Law Journal
Downloads: 85
[texts]The Supernova Relic Neutrino Backgrounds at KamLAND and Super-Kamiokande - Louis E. Strigari
We calculate the Supernova Relic Neutrino (SRN) background flux for the KamLAND and Super-Kamiokande (SK) detectors, motivated by the reduction in background at SK and new results for the star formation history (e.g., from the Sloan Digital Sky Survey (SDSS)). Our best estimate for the flux at SK is slightly below, but very close to the current SK upper limit. The SK upper limit is already inconsistent with a range of star formation histories allowed by the SDSS data...
Downloads: 17
[texts]Testing two nuclear physics approximations used in the standard leaky box model for the spallogenic production of LiBeB - J. P. Kneller
The spallative production rates of Lithium, Beryllium and Boron (LiBeB) are a necessary component in any calculation of the evolution of these nuclei in the Galaxy. Previous calculations of these rates relied on two assumptions relating to the nuclear physics aspects: the straight-ahead approximation that describes the distribution of fragment energies and the assumption that the major contributor to the production rate arises from single-step reactions between primary cosmic ray projectiles and...
Downloads: 7
[texts]The Spallagenic Production Rates of Lithium, Beryllium and Boron - J. P. Kneller
We calculate the production rates of Li6, Li7, Be9, B10 and B11 via spallation of Carbon, Nitrogen and Oxygen nuclei by protons and alpha-particles and by alpha-alpha fusion reactions. We include recent measurements of the cross sections of alpha-alpha fusion reactions and find that the computations yield rates of Li6 and Li7 production that are nearly a factor of two smaller than previously calculated...
Downloads: 15
[texts]Stellar Mixing and the Primordial Lithium Abundance - M. H. Pinsonneault
We compare the properties of recent samples of the lithium abundances in halo stars to one another and to the predictions of theoretical models including rotational mixing, and we examine the data for trends with metal abundance. We find from a KS test that in the absence of any correction for chemical evolution, the Ryan, Norris, & Beers (1999} sample is fully consistent with mild rotational mixing induced depletion and, therefore, with an initial lithium abundance higher than the observed valu...
Downloads: 5
[texts]Anisotropies in the gamma-ray sky from millisecond pulsars - Jennifer M. Siegal-Gaskins
Pulsars emerge in the Fermi era as a sizable population of gamma-ray sources. Millisecond pulsars (MSPs) constitute an older subpopulation whose sky distribution extends to high Galactic latitudes, and it has been suggested that unresolved members of this class may contribute a significant fraction of the measured large-scale isotropic gamma-ray background (IGRB). We investigate the possible energy-dependent contribution of unresolved MSPs to the anisotropy of the Fermi-measured IGRB...
Downloads: 8
[texts]Present-Day Descendants of z=3 Ly-α Emitting Galaxies in the Millennium-II Halo Merger Trees - Jean P. Walker Soler
Using the Millennium-II Simulation dark matter sub-halo merger histories, we created mock catalogs of Lyman Alpha Emitting (LAE) galaxies at z=3.1 to study the properties of their descendants. Several models were created by selecting the sub-halos to match the number density and typical dark matter mass determined from observations of these galaxies. We used mass-based and age-based selection criteria to study their effects on descendant populations at z~2, 1 and 0...
Downloads: 5
[texts]Direct X-ray Constraints on Sterile Neutrino Warm Dark Matter - Casey R. Watson
Warm dark matter (WDM) might more easily account for small scale clustering measurements than the heavier particles typically invoked in Lambda cold dark matter (LCDM) cosmologies. In this paper, we consider a Lambda WDM cosmology in which sterile neutrinos nu_s, with a mass m_s of roughly 1-100 keV, are the dark matter. We use the diffuse X-ray spectrum (total minus resolved point source emission) of the Andromeda galaxy to constrain the rate of sterile neutrino radiative decay: nu_s -> nu_{e,m...
Downloads: 2
[texts]Test-beds and applications for apparent horizon finders in numerical relativity - M. Alcubierre
We present a series of test beds for numerical codes designed to find apparent horizons. We consider three apparent horizon finders that use different numerical methods: one of them in axisymmetry, and two fully three-dimensional. We concentrate first on a toy model that has a simple horizon structure, and then go on to study single and multiple black hole data sets. We use our finders to look for apparent horizons in Brill wave initial data where we discover that some results published previous...
Downloads: 3
[texts]Halo Star Lithium Depletion - M. H. Pinsonneault
The depletion of lithium during the pre-main sequence and main sequence phases of stellar evolution plays a crucial role in the comparison of the predictions of big bang nucleosynthesis with the abundances observed in halo stars. In the past a wide range of possible depletion factors, ranging from minimal in standard (non-rotating) stellar models to as much as an order of magnitude in models including rotational mixing have been suggested...
Downloads: 4
[texts]Rotational Mixing And The Primordial Lithium Abundance - M. H. Pinsonneault
There has been recent progress in the study of the angular momentum evolution of low mass stars (Krishnamurthi et al 1997a). Theoretical models can now be constructed which reproduce the angular momentum evolution of low mass open cluster stars and the distribution of initial conditions can be inferred from young clusters. In this poster we report on the application of these models to the problem of rotational mixing in halo stars...
Downloads: 7
[texts]Predicting Big Bang Deuterium - N. Hata
We present new upper and lower bounds to the primordial abundances of deuterium and helium-3 based on observational data from the solar system and the interstellar medium. Independent of any model for the primordial production of the elements we find (at the 95\% C.L.): $1.5 \times 10^{-5} \le (D/H)_P \le 10.0 \times 10^{-5}$ and $(^3He/H)_P \le 2.6\times 10^{-5}$. When combined with the predictions of standard big bang nucleosynthesis, these constraints lead to a 95\% C.L...
Downloads: 38
[texts]The Concordance Cosmic Star Formation Rate: Implications from and for the Supernova Neutrino and Gamma Ray Backgrounds - Louis E. Strigari
We constrain the Cosmic Star Formation Rate (CSFR) by requiring that massive stars produce the observed UV, optical, and IR light while at the same time not overproduce the Diffuse Supernova Neutrino Background as bounded by Super-Kamiokande. With the massive star component so constrained we then show that a reasonable choice of stellar Initial Mass Function and other parameters results in SNIa rates and iron yields in good agreement with data...
Downloads: 4
[texts]How Does CMB + BBN Constrain New Physics? - James P. Kneller
Recent cosmic microwave background (CMB) results from BOOMERANG, MAXIMA, and DASI provide cosmological constraints on new physics that can be competitive with those derived from Big Bang Nucleosynthesis (BBN). In particular, both CMB and BBN can be used to place limits on models involving neutrino degeneracy and additional relativistic degrees of freedom. However, for the case of the CMB, these constraints are, in general, sensitive to the assumed priors...
Downloads: 6
[texts]Big Bang Nucleosynthesis Constraints on Brane Cosmologies - Jonathan D. Bratt
We examine constraints from Big Bang nucleosynthesis on type II Randall-Sundrum brane cosmologies with both a dark radiation component and a quadratic term that depends on the 5-dimensional Planck mass, M_5. Using limits on the abundances of deuterium and helium-4, we calculate the allowed region in the M_5-dark radiation plane and derive the precise BBN bound on M_5 alone with no dark radiation: M_5 > 13 TeV.
Downloads: 8
[texts]Big Bang Nucleosynthesis in Crisis? - N. Hata
A new evaluation of the constraint on the number of light neutrino species (N_nu) from big bang nucleosynthesis suggests a discrepancy between the predicted light element abundances and those inferred from observations, unless the inferred primordial 4He abundance has been underestimated by 0.014 +/- 0.004 (1 sigma) or less than 10% (95%C.L.) of 3He survives stellar processing. With the quoted systematic errors in the observed abundances and a conservative chemical evolution parameterization, th...
Downloads: 8
[texts]Production of A=6,7 Nuclides in the Alpha + Alpha Reaction and Cosmic Ray Nucleosynthesis - David J. Mercer
Cross sections for production of 6He, 6Li, 7Li, and 7Be in the alpha+alpha reaction were measured at bombarding energies of 159.3, 279.6, and 619.8 MeV, and are found to decrease rapidly with increasing energy. These cross sections are essential for the calculation of the rate of nucleosynthesis of the lithium isotopes in the cosmic rays and thereby play a key role in our understanding of the synthesis of Li, Be, and B...
Downloads: 4
[texts]APS Neutrino Study: Report of the Neutrino Astrophysics and Cosmology Working Group - Steve W. Barwick
In 2002, Ray Davis and Masatoshi Koshiba were awarded the Nobel Prize in Physics ``for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos.'' However, while astronomy has undergone a revolution in understanding by synthesizing data taken at many wavelengths, the universe has only barely been glimpsed in neutrinos, just the Sun and the nearby SN 1987A. An entire universe awaits, and since neutrinos can probe astrophysical objects at densities, energies, a...
Downloads: 5
[texts]Report of the Beyond the Standard Model Working Group of the 1999 UK Phenomenology Workshop on Collider Physics (Durham) - B. C. Allanach
The Beyond the Standard Model Working Group discussed a variety of topics relating to exotic searches at current and future colliders, and the phenomenology of current models beyond the Standard Model. For example, various supersymmetric (SUSY) and extra dimensions search possibilities and constraints are presented. Fine-tuning implications of SUSY searches are derived. The implications of Higgs (non)-discovery are discussed, as well as the program HDECAY...
Downloads: 2
[texts]Constraining Dark Energy with the Dark Energy Survey: Theoretical Challenges - James Annis
The Dark Energy Survey (DES) will use a new imaging camera on the Blanco 4-m telescope at CTIO to image 5000 square degrees of sky in the South Galactic Cap in four optical bands, and to carry out repeat imaging over a smaller area to identify and measure lightcurves of Type Ia supernovae. The main imaging area overlaps the planned Sunyaev-Zel'dovich survey of the South Pole Telescope. The idea behind DES is to use four distinct and largely independent methods to probe the properties of dark ene...
Downloads: 9
[texts]Nucleon form factors from high statistics mixed-action calculations with 2+1 flavors - LHPC Collaboration
We present new high-statistics results for nucleon form factors at pion masses of approximately 290, 350, 500, and 600 MeV using a mixed action of domain wall valence quarks on an improved staggered sea. We perform chiral fits to both vector and axial form factors and compare our results to experiment.
Downloads: 8
[texts]Milagro Constraints on Very High Energy Emission from Short Duration Gamma-Ray Bursts - A. A. Abdo
Recent rapid localizations of short, hard gamma-ray bursts (GRBs) by the Swift and HETE satellites have led to the observation of the first afterglows and the measurement of the first redshifts from this type of burst. Detection of >100 GeV counterparts would place powerful constraints on GRB mechanisms. Seventeen short duration (100 GeV counterparts to these GRBs and find no significant emission correlated with these bursts...
Downloads: 3
[texts]Milagro Observations of Multi-TeV Emission from Galactic Sources in the Fermi Bright Source List - A. A. Abdo
We present the result of a search of the Milagro sky map for spatial correlations with sources from a subset of the recent Fermi Bright Source List (BSL). The BSL consists of the 205 most significant sources detected above 100 MeV by the Fermi Large Area Telescope. We select sources based on their categorization in the BSL, taking all confirmed or possible Galactic sources in the field of view of Milagro...
Downloads: 5
[texts]Spectrum and Morphology of the Two Brightest Milagro Sources in the Cygnus Region: MGRO J2019+37 and MGRO J2031+41 - A. A. Abdo
The Cygnus region is a very bright and complex portion of the TeV sky, host to unidentified sources and a diffuse excess with respect to conventional cosmic-ray propagation models. Two of the brightest TeV sources, MGRO J2019+37 and MGRO J2031+41, are analyzed using Milagro data with a new technique, and their emission is tested under two different spectral assumptions: a power law and a power law with an exponential cutoff...
Downloads: 5
[texts]Observation and Spectral Measurements of the Crab Nebula with Milagro - A. A. Abdo
The Crab Nebula was detected with the Milagro experiment at a statistical significance of 17 standard deviations over the lifetime of the experiment. The experiment was sensitive to approximately 100 GeV - 100 TeV gamma ray air showers by observing the particle footprint reaching the ground. The fraction of detectors recording signals from photons at the ground is a suitable proxy for the energy of the primary particle and has been used to measure the photon energy spectrum of the Crab Nebula be...
Downloads: 3
[texts]Discovery of Localized Regions of Excess 10-TeV Cosmic Rays - A. A. Abdo
An analysis of 7 years of Milagro data performed on a 10-degree angular scale has found two localized regions of excess of unknown origin with greater than 12 sigma significance. Both regions are inconsistent with gamma-ray emission with high confidence. One of the regions has a different energy spectrum than the isotropic cosmic-ray flux at a level of 4.6 sigma, and it is consistent with hard spectrum protons with an exponential cutoff, with the most significant excess at ~10 TeV...
Downloads: 4
[texts]TeV Gamma-Ray Sources from a Survey of the Galactic Plane with Milagro - A. A. Abdo
A survey of Galactic gamma-ray sources at a median energy of ~20 TeV has been performed using the Milagro Gamma Ray Observatory. Eight candidate sources of TeV emission are detected with pre-trials significance $>4.5\sigma$ in the region of Galactic longitude $l\in[30^\circ,220^\circ]$ and latitude $b\in[-10^\circ,10^\circ]$. Four of these sources, including the Crab nebula and the recently published MGRO J2019+37, are observed with significances $>4\sigma$ after accounting for the trials involv...
Downloads: 3
[texts]The Large Scale Cosmic-Ray Anisotropy as Observed with Milagro - A. A. Abdo
Results are presented of a harmonic analysis of the large scale cosmic-ray anisotropy as observed by the Milagro observatory. We show a two-dimensional display of the sidereal anisotropy pro jections in right ascension generated by the fitting of three harmonics to 18 separate declination bands. The Milagro observatory is a water Cherenkov detector located in the Jemez mountains near Los Alamos, New Mexico...
Downloads: 2
[texts]A Measurement of the Spatial Distribution of Diffuse TeV Gamma Ray Emission from the Galactic Plane with Milagro - A. A. Abdo
Diffuse $\gamma$-ray emission produced by the interaction of cosmic-ray particles with matter and radiation in the Galaxy can be used to probe the distribution of cosmic rays and their sources in different regions of the Galaxy. With its large field of view and long observation time, the Milagro Gamma Ray Observatory is an ideal instrument for surveying large regions of the Northern Hemisphere sky and for detecting diffuse $\gamma$-ray emission at very high energies...
Downloads: 5
[texts]Stable characteristic evolution of generic 3-dimensional single-black-hole spacetimes - The Binary Black Hole Grand Challenge Alliance
We report new results which establish that the accurate 3-dimensional numerical simulation of generic single-black-hole spacetimes has been achieved by characteristic evolution with unlimited long term stability. Our results cover a selection of distorted, moving and spinning single black holes, with evolution times up to 60,000M.
Downloads: 15
[texts]Gravitational wave extraction and outer boundary conditions by perturbative matching - The Binary Black Hole Grand Challenge Alliance
We present a method for extracting gravitational radiation from a three-dimensional numerical relativity simulation and, using the extracted data, to provide outer boundary conditions. The method treats dynamical gravitational variables as nonspherical perturbations of Schwarzschild geometry. We discuss a code which implements this method and present results of tests which have been performed with a three dimensional numerical relativity code.
Downloads: 3
[texts]Boosted three-dimensional black-hole evolutions with singularity excision - The Binary Black Hole Grand Challenge Alliance
Binary black hole interactions provide potentially the strongest source of gravitational radiation for detectors currently under development. We present some results from the Binary Black Hole Grand Challenge Alliance three- dimensional Cauchy evolution module. These constitute essential steps towards modeling such interactions and predicting gravitational radiation waveforms. We report on single black hole evolutions and the first successful demonstration of a black hole moving freely through a...
Downloads: 3
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